DPP4 can cleave 2 amino acids off the end of a number of chemokines, rendering the chemokine inactive. Collaborators at the Pasteur institute were interested in what effect inhibiting DPP4 would have on the level of the active chemokine forms. Using a new assay developed by our collaborators, the level of full-length (active form) and cleaved (inactive) CXCL10 were measured in healthy individuals before and after administration of either sitagliptin or placebo. During active DPP4 inhibition while taking sitagliptin, individuals showed a decrease in full length CXCL10 and an increase in the shorter inactive form. Therefore, DPP4 has a dominant role for processing CXCL10 in vivo.